I’m replacing the spark plug wires with new and reusing some spark plug caps and boots that are in good condition. This isn’t a hard job and since the original spark plug wires have been in use for who knows how long, I want new wires.
All I used is spark plug wire ( 12 12 8 036 124 ) and new spark plugs (BOSCH W6DC). I reused the rest of the parts after cleaning them up.
Reusing Coil Sleeves
Here are all the parts I need.
I used some Forever Black on the rubber boots and “000” grade steel wool to polish up the metal exterior the spark plug caps. The boots at the top go on the spark plug caps and the ones on the bottom go over the center tower of the coils.The cable on the right is the old one with a coil sleeve, and the one I removed is next to it.
I use a small blade screwdriver to gently pry the ends of the sleeve away from the wires so I can slide them off. I don’t want to deform them very much, so I go slow.
Preparing New Plug Wire
I used the existing wire to cut the new wire to length which I measured as 20 inches. Note that the end of the wire that goes into the coil has insulation removed and there is bare wire that you should include in the total length.
I strip 1/2 inch of insulation being careful not to nick the copper strands.
I spread the stands out and fold them over the insulation. This will provide a solid connection with the metal sleeve when it’s crimped onto the outer insulation of the plug wire.
I slide the metal sleeve over the wire so the copper strands are on the back side of the sleeve. I use my pliers to crimp the two buttons on the top of the sleeve and the band at the bottom of the sleeve so the sleeve is firmly anchored on the insulator.
I install the rubber boot that slips over the tower in the center of the coil. Then I put some dielectric grease around the bottom of the sleeve insert the sleeve into the center tower of the coil until all of the sleeve is inside the tower.
The spark plug cap has a threaded pin inside the insulator. I put the rubber boot on the wire and then screw the spark plug cap on the end of the plug wire until it is hard to turn indicating the wire is fully inserted inside the insulator of the spark plug cap. I put some dielectric grease on the end of the insulator and then pull the boot over it.
I route the plug wires through the larger hole in the rubber tank gasket and then insert the caps onto the ends of the spark plugs.
I set the gap on the plugs, put a little antisieze on the threads and snug them into the spark plug holes being careful not to over tighten the plugs.
Finally, I put the red plastic tie around the bottom of the rubber cable and wire routing block and tighten it.
Here is the view from the saddle with the new plugs and plug wires installed along with the carburetors and new choke and throttle cables. It’s just about ready to fly again 🙂
Thanks for this, Brook! I’ve got an R75/6 and when I was washing it I noticed the spark plug wire had detached. Panic! Found your site and it was a very easy fix. But in mine it’s a friction fit where the wire is “impaled” on a serrated/barbed point inside the plug connector. Thanks again!
You’re welcome. I’m pleased this material helped you.
Thanks so much for the clear and concise attention to detail text w/excellent pics. I was wondering about the correct plug wire routing and especially attaching a new (used) plug wire at the coil for the cap failed one and am now better prepared. It seems that those specifics are identical or nearly so to those required for my 83 R80/RT.
I’m glad this proved helpful to you.
My new to me ‘75 R90/6 was occasionally stuttering at any rpm. All my valve adjustment, timing, points replacing and carb tuning wasn’t helping. One day, by chance, I fiddled with the right plug cap while it was idling, and KERBLAMMO! I got a nasty shock and saw it arc from the cap boot to the cylinder. Sure enough, I found the lead was almost completely detached from the plug cap. Thanks to your segment on this, 5 min of fixing (mine attach the way yours do in this article) has the bike running the best it has since I bought it in November! Thanks for the info on this, as well as your very detailed wiring diagram construction. I couldn’t have got the old girl running myself without your time and effort to publish the articles, and especially, as mentioned above, the pictures.
Many thanks Brook,
Sometimes the Gremlins are harder to find when they are standing right in front of you. 🙂 I’m pleased you found the source of your problem. And, thank you for you kind words.